This invention relates to a device for coupling moving blades of a steam turbine capable of effectively preventing the deformation and the vibration of the moving blades during operation.
Generally, when the moving blades of a steam turbine are rotated, they are subjected to a considerably large centrifugal force. Particularly, in recent years, there is required a steam turbine having a large capacity.
In such turbine, the length of the moving blades of the final stage becomes substantial and such long moving blades are subjected to a larger centrifugal force during the operation.
In such turbine, since the turbine blades in the final stage are constructed to be twisted longitudinally, the centrifugal force acts on the blades to deform, namely untwist, the blades. In addition, there is a problem that vibration of the turbine blades due to natural vibration and vibration due to an external force caused by steam impulse are generated when they are rotated at a high speed. Therefore, it is required to increase the efficiency for attenuating these vibrations.
Although it will be described in detail hereinafter in conjunction with the accompanying drawings, in a prior art, in order to eliminate the problems described above, the moving blades were interconnected in, for example, the following manners.
1. To fix all blades by using a wire and then weld them.
2. To provide projections on the inner and outer surfaces of the all blades and then weld the adjacent projections.
3. To connect the adjacent projections by using a coupling member.
However, these connecting methods have such problems as formation of cracks in the welded portions, a difficulty in firm welding of the projections and requirement of much time and work for assembling the coupling members.